JP2007315272A - Adjustable valve mechanism of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable and inexpensive structure to eliminate a play between a cam member 41 to be struck and a cam lobe 17 in an adjustable valve mechanism 3 of an internal combustion engine for adjusting the operating characteristics of a suction valve 14 of the internal combustion engine 1. <P>SOLUTION: In the adjustable valve mechanism 3, a slider gear 43 is outwardly provided on the periphery of a rocker shaft 31 in which a control shaft 32 is inserted axially displaceably, enabling interlocking with the control shaft 32. The control shaft 32 is axially displaced to change the relative phase difference of valve striking members 42A, 42B engaged with a side helical spline 43b of a slider gear 43 for the cam member 41 to be struck to be engaged with a center helical spline 43a of the slider gear 43. A plate spring 26 having a cantilever shape is attached to a cylinder head 12 side as an energizing means for pressing the cam member 41 to be struck onto the cam lobe 17 of the cam shaft 16. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable valve mechanism that varies the operating characteristics of an intake valve or an exhaust valve of an internal combustion engine.

  2. Description of the Related Art There is known a variable valve mechanism that varies operating characteristics such as valve lift and operating angle of intake valves and exhaust valves in accordance with the operating state of an internal combustion engine (see, for example, Patent Document 1).

  This variable valve mechanism has an intermediate drive mechanism arranged between the cam lobe and the valve, and this intermediate drive mechanism is linked to the axial movement of the control shaft inserted through the central hole of the rocker shaft. By rotating the input part (cam hitting member) and the two swing cams (valve striking member) relatively by the slider gear, the relative phase difference between them is changed and the lift amount of the valve is adjusted. It is like that.

  In addition, the outer periphery of the slider gear is provided with helical splines in three rows in the axial direction. An input portion is provided at the center helical spline of the slider gear, and two swing cams are provided at the two side helical splines of the slider gear. Are splined. The inclination directions of the two side helical splines are opposite to the center helical spline.

In operation, when the control shaft is displaced in the axial direction, the slider gear interlocking with the control shaft spirally rotates, so that the two rocking cams rotate relative to the input unit, and the relative phase difference between them changes. Is done.
JP 2001-263015 A

  In the above conventional example, there is a gap between the input portion and the base circle of the cam lobe due to the play of the meshing portion between the helical spline of the slider gear and the helical spline of the input portion and the helical spline of the swing cam. Therefore, it is considered to urge the input unit so as to press it against the cam lobe with an urging means.

  This urging means can be composed of a cylindrical coil spring, a case for holding it, and a member for supporting the case on the cylinder head side, etc., but it has a large number of parts and assembly steps, which causes an increase in cost. It has become. There is room for improvement here.

  An object of the present invention is to provide a highly reliable structure at a low cost that eliminates play between a cam hit member and a cam lobe in a variable valve mechanism of an internal combustion engine.

  The present invention is a variable valve mechanism that can change the operating characteristics of an intake valve or an exhaust valve of an internal combustion engine, and has a control shaft in a central hole of a rocker shaft fixedly supported in parallel with a camshaft on a cylinder head. The slider gear is fitted on the outer periphery of the rocker shaft so as to be interlocked with the control shaft, and the cam hitting member and the valve striking member are adjacent to the slider gear in the axial direction so that the inclination directions are opposite to each other. The cam hitting member is configured to change the relative phase difference of the valve hitting member with respect to the cam hitting member by externally disposing it through a helical spline, and displacing the control shaft in the axial direction. As a biasing means for biasing it against the cylinder head, it is mounted in a cantilever shape on the cylinder head side. It is characterized in that it comprises a leaf spring attached.

  According to this configuration, only a plate spring and a fastening member such as a bolt for stopping the plate spring are required. Therefore, a larger number of members are required for holding the coil spring than when the coil spring is used as in the conventional example. The number of parts and assembly man-hours can be reduced, such as being unnecessary. As a result, a highly reliable structure that eliminates play between the cam hit member and the cam lobe can be provided at a low cost.

  Preferably, the cam hitting member has a cylindrical shape, and a fork and a nose projecting radially outward are provided on an outer periphery of the cam hitting member, and a roller abutting on the cam lobe is rotatable on the fork. The leaf spring is configured such that the free end side of the leaf spring is brought into contact with the nose to urge the cam hit member in one rotation direction and press the roller against the cam.

  Thus, the shape of the cam hit member can be specified, and thereby the direction of action of the force of the leaf spring on the cam hit member becomes clear.

  Preferably, the base end side of the leaf spring has a long hole extending toward the free end side, and is bolted to the cylinder head through the long hole.

  According to this configuration, the distance from the bolting position on the base end side of the leaf spring to the contact position on the free end side can be changed in size, and the urging force of the leaf spring against the cam hit member can be arbitrarily set. It becomes possible to adjust. For example, if the distance is shortened, the urging force can be increased, and if the distance is increased, the urging force can be reduced.

  As a result, the versatility of the leaf springs is increased, for example, the leaf springs can be commonly used regardless of differences in the specifications of the internal combustion engine.

  Preferably, the leaf spring is widened from the free end side toward the base end side.

  According to this configuration, considering that the stress acting on the base end side of the leaf spring is larger than the stress acting on the free end side, the strength on the base end side is improved as necessary. .

  In this case, it is possible to design an equal stress to make the stress acting from the base end side of the leaf spring to the free end side substantially equal, and the strength is increased by making the base end side of the leaf spring wider. Can be made into a relatively low-strength and inexpensive material, which can contribute to further cost reduction.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the reliable structure which eliminated the play between a cam hitting member and a cam at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 12 show an embodiment of the present invention.

  First, prior to the description of the portion to which the features of the present invention are applied, the configuration of a variable valve mechanism for an internal combustion engine which is a premise of the present invention will be described. Here, as shown in FIGS. 1 and 2, an in-line four-cylinder DOHC engine is used as the internal combustion engine 1, and a four-valve type with two intake valves 14 and two exhaust valves 15 per cylinder is taken as an example. In this example, the variable valve mechanism 3 is attached to two intake valves 14 and 14 per cylinder in the internal combustion engine 1. The exhaust valve 15 can be similarly configured to be driven using the variable valve mechanism 3, but the description here is omitted for the sake of simplicity.

  The variable valve mechanism 3 can continuously change the valve lift amount and the operating angle of the intake valves 14 and 14, and the configuration thereof is described in detail in, for example, Japanese Patent Application Laid-Open No. 2001-263015. However, for example, as shown in FIGS. 1 to 10, a rocker shaft 31, a control shaft 32, an actuator 33, a valve lift mechanism 4, and the like are provided.

  The variable valve mechanism 3 is disposed between the cam lobe 17 of the intake camshaft 16 and the roller rocker arm 24. One end of the roller rocker arm 24 is supported by the lash adjuster 25 and the other end is in contact with the tappet 14 a at the upper end of the intake valve 14. The roller rocker arm 24 is a so-called end pivot type in which a roller 24a is rotatably supported in the middle in the longitudinal direction. The lash adjuster 25 is, for example, a hydraulic type, and has a known configuration that functions to always keep the tappet clearance of the intake valve 14 at zero.

  The rocker shaft 31 is supported by a large number of partition walls 21 provided at regular intervals on the cylinder head 12 so as to be immovable in the axial direction and the circumferential direction. The rocker shaft 31 is arranged in parallel with the intake camshaft 16 and the exhaust camshaft 18, that is, along the arrangement direction of the cylinders (combustion chambers 13).

  The control shaft 32 is inserted into the center hole of the rocker shaft 31 formed of a hollow pipe so as to be axially displaceable, and is driven forward and backward in the axial direction by the actuator 33.

  The number of valve lift mechanisms 4 is the same as the number of cylinders, and is externally mounted on the rocker shaft 31 so as to correspond to each cylinder. The valve lift mechanism 4 includes an input arm 41 as a cam hitting member, two output arms 42A and 42B as a valve hitting member, and a slider gear 43.

  The input arm 41 has a cylindrical housing 41 a, and a helical spline 41 b that meshes with the input-side helical spline 43 a of the slider gear 43 is formed on the inner peripheral surface thereof.

  In the input arm 41, a pair of forks 41cL and 41cR projecting radially outward is provided on the outer periphery of the housing 41a, and a support shaft parallel to the rocker shaft 31 is provided between the pair of forks 41cL and 41cR. A roller 41e is rotatably fitted and supported on the support shaft 41d.

  The output arms 42A and 42B both have a cylindrical housing 42a, and a helical spline 42b that meshes with the output-side helical spline 43b of the slider gear 43 is formed on the inner peripheral surface thereof. A nose 42c protruding outward in the radial direction is provided on the outer periphery of the housing 42a of the output arms 42A and 42B. The nose 42c is formed in a substantially triangular shape in a side view, and a cam surface 42d is provided on one side thereof.

  The slider gear 43 is externally mounted on the rocker shaft 31 so as to be movable in the axial direction in conjunction with the control shaft 32, and the input arm 41 and the two output arms 42A and 42B are externally mounted on the outer diameter side thereof. .

  The slider gear 43 is formed in a cylindrical shape having a through-hole 43c in the center, and an input side helical spline 43a that meshes with the helical spline 41b of the input arm 41 is formed in the middle in the axial direction on the outer periphery. Output side helical splines 43b that mesh with the helical splines 42b of the output arms 42A and 42B are formed on both sides in the axial direction.

  The output side helical spline 43b has a smaller outer diameter than the input side helical spline 43a. The input-side helical spline 43a and the output-side helical spline 43b are formed so that the inclination directions of the teeth are opposite.

  The input arm 41 is swung by the rotation of the cam lobe 17, and the intake valve 14 is lifted via the roller rocker arm 24 by the output arms 42 </ b> A and 42 </ b> B that swing integrally with the input arm 41. Yes. The roller 24a of the roller rocker arm 24 is pressed against either the base circular portion of the housing 42a of the output arms 42A and 42B or the cam surface 42d of the nose 42c by the valve spring 14b of the intake valve 14.

  Here, the coupling form of the slider gear 43 to the rocker shaft 31 and the control shaft 32 will be described with reference to FIGS.

  In order to connect the slider gear 43 fitted to the rocker shaft 31 to the control shaft 32 in the rocker shaft 31 so as to be able to transmit power, the slider gear 43 has an inner circumferential groove 43d with a partial arc shape in a longitudinal section. A bushing 46 is provided.

  The bush 46 is formed with a pin insertion hole (through hole) 46 a in the middle in the circumferential direction, and is connected to the control shaft 32 via a connect pin 44.

  Specifically, the distal end portion of the connect pin 44 is inserted into the pin insertion hole 46 a of the bush 46, and the distal end portion of the connect pin 44 is inserted into the pin insertion hole 32 a of the control shaft 32. An intermediate portion of the connect pin 44 is inserted into the long hole 31 a of the rocker shaft 31.

  The slider gear 43 assembled in this way operates as follows.

  The control shaft 32 is movable in the axial direction with respect to the rocker shaft 31 within the range of the axial length of the long hole 31 a of the rocker shaft 31. Further, the slider gear 43 is fixed in the axial position with respect to the control shaft 32 by the engagement between the inner circumferential groove 43 d and the bush 46.

  Therefore, when the control shaft 32 is moved in the axial direction by driving the actuator 33, the operation is transmitted to the slider gear 43 via the connect pin 44 and the bush 46. As a result, the slider gear 43 moves in the axial direction in conjunction with the control shaft 32.

  In addition, since the bush 46 is movable in the circumferential direction in the inner circumferential groove 43d of the slider gear 43, the slider gear 43 is rotatable with respect to the control shaft 32 within the range. Thus, when the control shaft 32 is moved in the axial direction, the slider gear 43 rotates with respect to the control shaft 32 while moving in the axial direction.

  When the torque of the intake camshaft 16 is transmitted to the input arm 41, the torque is transmitted from the input arm 41 to the output arms 42A and 42B via the slider gear 43. At this time, the slider gear 43 It swings around the rocker shaft 31.

  In such a valve lift mechanism 4, the slider gear 43 is moved in the axial direction together with the control shaft 32, and the relative position in the axial direction between the slider gear 43 and the input arm 41 and the output arms 42A and 42B is changed. Twisting forces in opposite directions are applied to the input arm 41 and the output arms 42A and 42B. As a result, the input arm 41 and the output arms 42A and 42B rotate relative to each other, and the relative phase difference between the roller 41e of the input arm 41 and the nose 42c of the output arms 42A and 42B is changed.

  In the variable valve mechanism 3, the valve lift mechanism 4 for each cylinder is fixed to a common control shaft 32, so that all cylinders are moved along with the axial movement of the control shaft 32. The lift amount of the intake valve 14 is simultaneously changed. However, the valve lift mechanism 4 for each cylinder can be operated individually.

  Next, the operation of the variable valve mechanism 3 will be described.

  As shown in FIG. 9A, when the base circle portion of the cam lobe 17 is in contact with the roller 41e of the input arm 41, the roller 24a of the roller rocker arm 24 moves to the base circle portion of the housing 42a of the output arms 42A and 42B. Is in contact with. Therefore, the intake valve 14 is maintained in a state where the lift amount is “0” (a state where the intake port 12a is closed).

  When the roller 41e of the input arm 41 is pushed down through the lift portion of the cam lobe 17 with the clockwise rotation of the intake camshaft 16, the input arm 41 is counterclockwise with respect to the rocker shaft 31 as shown in FIG. It rotates in the turning direction (arrow A direction). As a result, the output arms 42A and 42B and the slider gear 43 rotate together.

  As a result, the cam surface 42d formed on the nose 42c of the output arms 42A and 42B comes into contact with the roller 24a of the roller rocker arm 24, and the roller 24a is pushed down by the pressing of the cam surface 42d.

  As shown in FIG. 9B, when the roller 24a of the roller rocker arm 24 is pressed by the cam surface 42d, the roller rocker arm 24 swings around the contact portion with the lash adjuster 25, and the intake valve 14 The valve is opened.

  When the control shaft 32 is moved to the maximum in the direction away from the actuator 33 (the direction of arrow F in FIG. 3), the roller 41e of the input arm 41 and the nose of the output arms 42A and 42B around the axis of the rocker shaft 31. The relative phase difference from 42c is maximized.

  As a result, when the cam lobe 17 pushes down the roller 41e to the maximum, the displacement difference of the roller 24a of the roller rocker arm 24 becomes the largest, and the intake valve 14 is opened and closed with the maximum valve lift and operating angle.

  As shown in FIG. 10A, when the base circle portion of the cam lobe 17 is in contact with the roller 41e of the input arm 41, the contact position between the output arms 42A and 42B and the roller 24a is maximum from the cam surface 42d. It's far from the limit. When the roller 41e of the input arm 41 is pushed down by the lift portion of the cam lobe 17 by the rotation of the intake camshaft 16, the input arm 41 and the output arms 42A and 42B rotate together.

  However, in this case, since the contact position between the output arms 42A and 42B and the roller 24a is farthest from the cam surface 42d, the output until the pressing of the roller 24a of the roller rocker arm 24 by the cam surface 42d is started. The amount of rotation of the arms 42A and 42B is larger than that in the operating state shown in FIG. Further, when the roller 41e of the input arm 41 is pushed down through the lift portion of the cam lobe 17, the range of the cam surface 42d that comes into contact with the roller 24a is reduced to only a part of the base end side of the nose 42c. For this reason, the rocking | fluctuation amount of the roller rocker arm 24 according to the depression of the roller 41e by the lift part of the cam lobe 17 becomes small.

  As shown in FIG. 10B, the intake valve 14 is opened with a smaller valve lift amount due to the small swing amount of the roller rocker arm 24.

  Further, when the control shaft 32 is moved to the maximum in the direction approaching the actuator 33 (the arrow R direction in FIG. 3), the relative phase difference between the roller 41e and the nose 42c around the axis of the rocker shaft 31 is minimum. Become.

  As a result, the displacement amount of the roller 24a when the cam lobe 17 pushes the roller 41e down to the maximum is minimized, and the intake valve 14 is opened and closed with the minimum valve lift amount and operating angle.

  10 shows a case where the maximum lift amount of the intake valve 14 is “0”. Therefore, even when the cam lobe 17 pushes down the roller 41e to the maximum, as shown in FIG. The lift amount of the intake valve 14 is maintained at “0”.

  Next, portions to which the features of the present invention are applied will be described with reference to FIGS. In the figure, only one valve lift mechanism 4 is shown for easy understanding.

  In the valve lift mechanism 4 of the variable valve mechanism 3 described above, the urging means (see FIG. 2) for urging the input arm 41 to be pressed against the cam lobe 17 of the intake camshaft 16 has the following configuration. .

  In this embodiment, a leaf spring 26 is used as the biasing means. Specifically, as shown in FIG. 12, the leaf spring 26 has a strip shape and is set to have a substantially uniform width from one end side in the longitudinal direction to the other end side.

  As shown in FIG. 11, one end side in the longitudinal direction of the leaf spring 26 is attached in a cantilevered state in a substantially horizontal posture at an appropriate position of the cylinder head 12, and the other end side in the longitudinal direction can be freely displaced. It has become. The free end of the leaf spring 26 is in contact with the nose 41 f of the input arm 41, whereby the roller 41 e of the input arm 41 is pressed against the cam lobe 17 of the intake camshaft 16.

  A long hole 26a that is long in the longitudinal direction is formed through one end side in the longitudinal direction of the leaf spring 26, that is, the base end side, in the thickness direction. The long hole 26 a is used as an insertion hole for the bolt 27 when the leaf spring 26 is attached to the cylinder head 12 with the bolt 27.

  Then, by changing the position of the bolt 27 in the long hole 26a, the distance L from the stop position X of the bolt 27 on the proximal end side of the leaf spring 26 to the contact center position Y with respect to the input arm 41 on the free end side is increased or decreased. Thus, the biasing force of the leaf spring 26 against the input arm 41 can be arbitrarily adjusted.

  Incidentally, if the distance L is shortened, the urging force by the leaf spring 26 can be increased, and if it is made longer, the urging force by the leaf spring 26 can be reduced. Thereby, the versatility of the leaf spring 26 is increased, for example, the leaf spring 26 can be commonly used regardless of the specification difference of the internal combustion engine.

  The leaf spring 26 described above can be made of, for example, spring steel or phosphor bronze, but is not particularly limited as long as it has predetermined strength and toughness.

  Incidentally, it is possible to adjust the initial urging force of the spring 26 against the input arm 41 by changing the posture of the leaf spring 26.

  That is, if the leaf spring 26 is left in a natural state where it is not elastically deformed in a substantially horizontal posture, the roller 41e of the input arm 41 is merely brought into contact with the cam lobe 17 so that the elastic force is not biased. it can. However, for example, as shown in FIG. 13, when the posture of the leaf spring 26 is bent like a bow so that its free end side is warped upward, the elastic force of the leaf spring 26 caused by this warpage causes the roller 41e of the input arm 41 to move. Can be brought into strong contact with the cam lobe 17.

  Naturally, the elastic restoring force of the leaf spring 26, that is, the biasing force against the input arm 41, becomes stronger as the amount of warping of the leaf spring 26 is increased, and becomes weaker as the amount of warping is reduced.

  As described above, according to the embodiment to which the present invention is applied, the leaf spring 26 and the bolt 27 that stops the plate spring 26 are used as the urging means for urging the input arm 41 to be pressed against the cam lobe 17 of the intake camshaft 16. Therefore, the number of parts and the number of assembling steps can be reduced because a large number of members necessary for holding the coil spring are not required as compared with the case where the coil spring is used as in the conventional example.

  Therefore, a highly reliable structure that eliminates play between the input arm 41 and the cam lobe 17 can be provided at a low cost.

  Hereinafter, other embodiments of the present invention will be described.

  (1) In the above embodiment, the leaf spring 26 has a uniform width from the free end side to the base end side. However, for example, as shown in FIG. It is possible to make it gradually widened toward.

  In consideration of the fact that the stress acting on the base end side of the leaf spring 26 in the installed state is larger than the stress acting on the free end side, the shape on the base end side requires the strength on the base end side. This is to improve it accordingly.

  In this case, since it is possible to design an equal stress to make the stress acting from the base end side of the leaf spring 26 to the free end side substantially equal, the base end side of the leaf spring 26 is widened to increase the strength. The material can be made a relatively low-strength and inexpensive material, which can contribute to further cost reduction.

It is a top view showing typically an internal-combustion engine provided with a variable valve mechanism concerning the present invention. It is an arrow view of the (2)-(2) line cross section of FIG. It is a perspective view of the variable valve mechanism of FIG. It is a disassembled perspective view of the valve lift mechanism of FIG. It is a perspective view which decomposes | disassembles and shows the slider gear and rocker shaft of the valve lift mechanism of FIG. It is a perspective view which fractures | ruptures and shows the upper half of the valve lift mechanism of FIG. FIG. 5 is a cross-sectional view showing a connecting portion of a slider gear to the rocker shaft and control shaft of FIG. 4. FIG. 8 is a cross-sectional view taken along line (8)-(8) in FIG. 7. FIG. 3 is a side view used for explaining the operation when the relative phase difference between the input arm and the output arm in FIG. 2 is maximized. FIG. 3 is a side view used for explaining the operation when the relative phase difference between the input arm and the output arm in FIG. 2 is minimized. It is a figure which expands and shows the input arm and leaf | plate spring in FIG. It is a top view of FIG. It is a figure which shows the state which bent the leaf | plate spring of FIG. 11 in the shape of a bow. It is a figure which shows the application example of the leaf | plate spring of FIG.

Explanation of symbols

1 Internal combustion engine
12 Cylinder head
14 Intake valve
15 Exhaust valve
16 Intake camshaft
17 Cam Rob
26 leaf spring
26a long hole
27 volts
3 Variable valve mechanism
31 Rocker shaft
32 Control shaft
33 Actuator
4 Valve lift mechanism
41 Input arm (cam hitting member)
41cL, 41cR Input arm nose
41f Nose of input arm
42A First output arm (valve striking member)
42B Second output arm (valve striking member)
43 Slider gear

Claims (4)

A variable valve mechanism capable of changing the operating characteristics of an intake valve or an exhaust valve of an internal combustion engine,
A control shaft is inserted in the center hole of the rocker shaft fixedly supported on the cylinder head in parallel with the camshaft so as to be axially displaceable, and a slider gear is mounted on the outer periphery of the rocker shaft so as to be interlocked with the control shaft. A cam hitting member and a valve hitting member are externally mounted on a slider gear through a helical spline whose axial direction is adjacent to each other in the axial direction, and the control shaft is displaced in the axial direction so that the valve hitting member with respect to the cam hitting member It is configured to change the relative phase difference of
A variable valve for an internal combustion engine comprising a leaf spring attached to the cylinder head side in a cantilevered manner as urging means for urging the cam hit member to be pressed against the cam lobe of the cam shaft. mechanism. The variable valve mechanism for an internal combustion engine according to claim 1,
The cam hitting member has a cylindrical shape, and a fork and a nose projecting radially outward are provided on an outer periphery of the cam hitting member, and a roller abutting on the cam is rotatably supported on the fork. ,
A variable valve for an internal combustion engine characterized in that the free end side of the leaf spring abuts on the nose to urge the cam hit member in one rotation direction and press the roller against the cam lobe. mechanism. The variable valve mechanism for an internal combustion engine according to claim 1 or 2,
A variable valve mechanism for an internal combustion engine having a long hole on the base end side of the leaf spring toward the free end and bolted to the cylinder head side through the long hole. The variable valve mechanism for an internal combustion engine according to any one of claims 1 to 3,
The variable valve mechanism for an internal combustion engine, wherein the leaf spring is widened from the free end side toward the base end side.

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